Snap fastening explosive increments to the boom of a projectile



Sept 20, 1955 P. G. GARRAHAN SNAP F' ASTENING EXPLOSIVE INCREMENTS TO THE BOOM OF A PROJECTILE Filed Dec. 10, 1953 INVENTOR.

Philip E- E'umnhnn d JIV'ATTORNEY'S' Patented sept. 2o, 1955 fire SNAP FASTENHNG EXPLSWE ENCREMENTS T0 THE BGlti F A PRJECTILE Philip G. Garrahan, Bloomfield, N. E., assigner to the United States of America as represented by the lSecretary of the Army Application December 10, 1953, Serial No. 397,494

5 Claims. (Cl. 162-49) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

The present invention relates to means for securing propellent increments to mortar projectiles.

Mortar projectiles of the type for which the present nvention is intended, are in the category of semi-fixed ammunition with the propelling charges formed as increments to be fastened externally of the projectile about the portion which may be referred to as the projectile boom. The number of increments used may vary with the required range or distance to a designated target. As a general rule each round comprises a fusiform fused projectile with a fin assembly, an ignition cartridge, and a percussion primer for initiating the ignition cartridge. The propelling increments are secured about the boom portion which is also formed as an ignition cartridge container, and each of the increments is set-off by flash from the ignition cartridge emitted through vents provided in the cartridge container.

Previous devices utilized for assembling the increments about the projectile have been found objectionable for one reason or another. ln a preferred method, the charges or increments are preformed toroidal, or doughnut-shaped blocks which obviously must be placed about the boom portion prior to assembly of the projectile, thereby giving rise to problems of assembly, disassembly, packaging and shipment to the point of use. Additionally considerable expense is entailed in the casting and formation of the individual increments.

As an improvement on the above method, horse-shoe 4 shaped resilient increments have been devised which may be contorted and forced into place about the projectile boom after the projectile is assembled. This latter expedient, of course, eliminates the problems concomitant with assembly, disassembly, shipment and use o f the projectiles. However the considerable expense of preforming the blocks is not obviated.

It is accordingly an object of this invention to provide means for fastening propellent increments to mortar projectile, which are free of the defects noted in prior art devices for accomplishing the Asame result.

A paramount purpose of this invention is to provide fastening devices for securing increment bags .to the booms of mortar projectiles, which are cheap to manufacture, easy to install, and which permit the assembly and disassembly of the bags on an assembled projectile in a simpler and more expeditious manner.

In the direction last named a strong and impelling need is to provide fastening devices for assembling bags on mortar projectile which permits the storing and shipping of the propellent increments separate from the projectile per se, and which insures the iirm, ready and facile placement of the bags in place immediately prior to use of the projectile.

A further and important consideration is the provision of means to secure propellent bags to projectiles which avoids the deposition in the launcher tube of objectionable particles from the metallic fastening devices.

An attainment sought is the provision of fastening devices to secure increment bags to mortar projectiles in a manner to eliminate the need for preforming and precasting doughnut-shaped or horseshoe-shaped propellent blocks, thereby saving the considerable expense involved in the manufacture of the preformed blocks.

Additional objects, advantages and features of the invention reside in the construction, arrangement Vand combination of parts involved in the embodiment of the invention as will appear from the following description and accompanying drawings, wherein:

Figure. l is a partial side elevation of the pertinent portion of a mortar projectile with increment bags held in place by the securing means of the invention.

Figure 2 is a longitudinal section of the projectile according to Figure 1.

Figure 3 is a transverse section taken on line 3-3 of Figure l, and

Figure 4 is a transverse section taken on line 4-4 of Figure l.

Referring again to the drawing wherein the same reference characters have been used to denote like or similar parts in the several views, reference character 1 designates a fusiform mortar projectile generally having the usual frontal ogive, and central bourrelet section, which parts are not pertinent to the invention and have not been shown. The central bourrelet merges into a rearwardly tapering rear portion 2, provided with a rearwardly extending reduced section 3 having external threads 4, the projectile per se being hollowed out forwardly of scction 3 to form a chamber 5, symmetrical about the longitudinal axis to receive an explosive charge 6, as is well known.

The boom section which is utilized to house the ignition cartridge comprises a rearwardly tapering section 7, merging with the taper of the portion 2, and provided in its forward face with a recess 8 provided with threads to screW-threadedly mate with the threads 4. Tapering section 7 ends in a rearwardly extending reduced portion 9, externally threaded at 10 to be screw-threadedly received in a recess 11 formed in a rearwardly extending cylindrical section 12, which is the hub of a lin assembly 13, later te be described.

The forward half of boom 7 is provided with an elongated axial chamber 14 extending rearwardly of recess 8, for housing an ignition cartridge 15, there being an axial flash 16 extending throughout the rearward half of the boom and communicating at its forward end with chamber 14. Boom 7 is also provided with several sets (4 sets shown) of axially spaced holes or vents 17, each vent extending radially outwardly between the side wall of chamber 14 and the outer periphery of boom 7, each set providing equally angular Vspacing for each individual vent therein relative tothe adjacent vent in its respective circumference.

The iin assembly 13 comprises the before-mentioned hub 12 about which are secured in equally angular-ly spaced relation, longitudinally extending radial fins 18, encircled about their rearward ends by a streamlined shroud 19 in the well known manner. Hub 12 is provided with an axial ash passage 20 communicating at its forward end which flash passage 16 and at its rearward end with an axial recess 21 of enlarged diameter having the rear portion of its inner wall threaded as at 21a, and into which is received an insert 22 ending forwardly of the rearmost extent of recess 21, and provided rearwardly with an externally threaded reduced portion 23. A bushing 24 having internal threads 25 to mate with the threads on reduced portion 23, and external threads 26 to mate with threads 21a occupies the remaining rearmost portion of recess 21 to provide a ush rear surface of hub 12 in radial alinement with the rearmost lateral edge of shroud 19.

Insert 22 is provided with a recess 27 to receive a relay 28, there being an axial ash passage 29 communicating at its forward end with recess 27, and at its rear end with a second recess 30 in insert 22 which continues rearwardly to the rear face of bushing 24. A percussion responsive primer 31 is received in the forward end of recess 30, and a firing pin 32 in the rear end thereof.

The devices for fastening the increment bags about the projectile comprise the well known male and female snap fastening devices and are clearly illustrated in Figure 2, 3 and 4. The female members are formed integral with the boom and comprise a rst forward plurality or set formed in the peripheral surface and concentric about the forward end of the boom section and a second plurality or set 41 also formed in the peripheral surface of the boom section and immediately forward of rear reduced portion 9 of the boom. Each of sets 40 and 41 comprises a plurality of equally angularly spaced outer cylindrical bores 42 and inner cylindrical bores 43 of smaller diameter forming a shoulder 44 therebetween. An insert 4S which is formed as a T in longitudinal cross section is snugly received in each of the bores 42 and 43, with shoulder 44 engaging a at inner surface of the T to limit the inner travel of the insert, and to ensure that each insert is equally depressed within the boom. Each insert 45 is provided with a spheroided cavity 46 to receive a corresponding male fastener head 47 of slightly enlarged diameter secured to the forward and rear end of the increment 48 in the well known manner. Each head 47 is provided with crossed grooves 49 to insure the proper resiliency and give so that the rnale head 47 may be snapped in place and held fast by the female portion of the fastener, as is commonly well known.

Each propelling increment comprises the bag 48 made of cellophane, cotton cloth properly water-proofed, or the like. The cloth is folded over and stitched longitudinally along one edge to form the before-mentioned tubular bag 48. Each bag is then lled with propellent powder 50 and then stitched rearwardly and forwardly of the forward and rear edges respectively, as at 51, 52, to form flaps 53, 54, thereby retaining powder 50 in the bag portion intermediate the flaps. The male fasteners 47 are then secured in any convenient manner to flaps 53, 54 and in position to conveniently n`t into a corresponding spheroidal cavity 46.

The male portion 47 of the snap fastener is preferably formed of a consumable plastic substance such as Celluloid or Pyralin to insure that the mortar tube remain free of metal deposits. However it is well within the purview of this invention also to utilize only suitable metallic substance instead, since it is believed that the amount of metal deposited would be infinitesimal or almost nonexistent.

Although each bag is illustrated as being tapered rearwardly to compensate for the rearward taper of the projectile, it is obvious that the increments may be made tubular, and approximately of pencil thickness, the only requirement being that each bag overlie a vent 17 so that it may be ignited. A projectile having a cylindrical instead of a tapered boom may also be used, and

although the exemplary illustration depicts a mortar projectile, other projectiles requiring externally mounted increments also fall within the purview of the instant invention. Other obvious modifications of the structure disclosed herein may also be resorted to without departing from the spirit and scope of the invention set forth in the subjoined claims.

I claim:

l. In combination with a fusiform mortar projectile having a rearwardly tapering tail section, defining a first rearwardly extending threaded tenon integral with said tail section, a rearwardly tapering boom having an external surface merging with the surface of said tail section, there being a recess formed in the forward face of said boom for threadedly engaging said first tenon, said boom including a second threaded tenon extending from the rearward end thereof, a fin assembly having a cylindrical hub, there being a threaded recess formed in the forward face of said hub to receive said second threaded tenon, a rst plurality of female snap fasteners equiangularly disposed about the forward end of said boom, a second plurality of female snap fastener members equiangularly disposed about the rear end of said boom, a plurality of elongated tubular propellent increments having flaps formed on the opposed ends thereof, a male snap fastener member secured to each flap, each said male member adapted to be received in a corresponding female member in said first and second pluralities, respectively.

2. The combination in claim l, each female snap fastener member in said first plurality being in longitudinal alinement with a corresponding female snap fastener member in said second plurality.

3. The combination in claim l, there being an axially elongated chamber formed in said boom, an ignition cartridge received in said chamber, there being a plurality of vents extending radially between said chamber and the external surface of said boom, each of said increments overlying at least one of said vents.

4. The combination in claim 3, and including a percussive responsive detonatable means in said hub for initiating said cartridge.

5. In combination with a mortar projectile having a rearwardly tapered boom section, a first plurality of female snap fastener elements circumferentially disposed about said section at one end thereof, a second plurality of female snap fastener elements circumferentially disposed about said section at the other end thereof in axially-spaced relation with said first plurality, a plurality of elongated tubular propellent containers each having flaps at its respective ends, one male snap fastener element secured to each flap, the male fastener elements of each container being adapted for securement to a corresponding axially aligned pair of female elements of said rst and second pluralities.

References Cited in the le of this patent UNITED STATES PATENTS 1,330,144 Sherman Feb. 10, 1920 2,062,495 Brayton Dec. l, 1936 2,412,593 Adelman Dec. 17, 1946 

